'Joint effort' to halt spread of wilding trees

National wilding conifer control programme manager Sherman Smith says collaboration is stopping the spread of the high-country pest. Photo / David Hill

Community collaboration is helping to halt the spread of wilding conifers in the South Island's high country.

The Ministry for Primary Industries (MPI) national wilding conifer control programme was ''a really great example of partnership working well'', programme manager Sherman Smith told farmers at Federated Farmers' South Island High Country Conference, held in Hanmer Springs on Friday, May 26.

Controlling the ''woody weed'' was a complex issue ''requiring co-ordination across multiple parties'', including the MPI, Department of Conservation, Land Information New Zealand, regional councils, the New Zealand Defence Force, Federated Farmers, local farmers and other local groups.

''This a big problem for New Zealand and it's too big for any one property owner to tackle alone, so it needs to be a joint effort.

''Conifers actually play a valuable role for New Zealand in timber exports, but in the wrong place they can have significant impacts on local ecology and many of you are feeling the pain of that.''

The four-year programme began last year and has involved eradicating wilding pines in 14 management units across 1.17 million hectares of high-country land, including Molesworth Station (near Hanmer Springs), the Amuri and Lewis Pass areas (Hurunui district), Porters Pass and Craigieburn (Selwyn district), Hakatere (Mid Canterbury), Four Peaks and Godley (South Canterbury) and St Mary-Ida (Waitaki district).

The 14 management units also included land in Kaimanawa (central North Island), Dunstan (Central Otago), Kawarau, Northern Eyre and Remarkables (Queenstown Lakes district) and Five Rivers (Northern Southland).

MPI senior policy adviser Alan Tinnelly said the main control methods had included aerial spraying, ground control, controlled burning and machine excavation.

While spraying had produced some good results, with ground control usually following a blanket aerial spray, in some areas using machinery such as a bulldozer to clear a site and turning it into grazing land was a more effective option, he said.

''I think we've made a really good start with 1.17 million hectares, but this isn't going to solve it - it's a long-term view.

''The government focus is that everyone needs to contribute to this work, so I encourage you to go back and talk to your neighbours to get them on board.''

Farmers should consider what trees they were planting on their property, particularly in shelter belts, and invest in trees which were unlikely to spread.

There were studies looking at developing sterile trees.